/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ForwardingObject;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.util.Collection;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An executor service which forwards all its method calls to another executor service. Subclasses
 * should override one or more methods to modify the behavior of the backing executor service as
 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * @author Kurt Alfred Kluever
 * @since 10.0
 */
@CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingExecutorService extends ForwardingObject
        implements ExecutorService
{
    /**
     * Constructor for use by subclasses.
     */
    protected ForwardingExecutorService()
    {
    }

    @Override
    protected abstract ExecutorService delegate();

    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException
    {
        return delegate().awaitTermination(timeout, unit);
    }

    @Override
    public <T extends @Nullable Object> List<Future<T>> invokeAll(
            Collection<? extends Callable<T>> tasks) throws InterruptedException
    {
        return delegate().invokeAll(tasks);
    }

    @Override
    public <T extends @Nullable Object> List<Future<T>> invokeAll(
            Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
            throws InterruptedException
    {
        return delegate().invokeAll(tasks, timeout, unit);
    }

    @Override
    public <T extends @Nullable Object> T invokeAny(Collection<? extends Callable<T>> tasks)
            throws InterruptedException, ExecutionException
    {
        return delegate().invokeAny(tasks);
    }

    @Override
    public <T extends @Nullable Object> T invokeAny(
            Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
            throws InterruptedException, ExecutionException, TimeoutException
    {
        return delegate().invokeAny(tasks, timeout, unit);
    }

    @Override
    public boolean isShutdown()
    {
        return delegate().isShutdown();
    }

    @Override
    public boolean isTerminated()
    {
        return delegate().isTerminated();
    }

    @Override
    public void shutdown()
    {
        delegate().shutdown();
    }

    @Override
    public List<Runnable> shutdownNow()
    {
        return delegate().shutdownNow();
    }

    @Override
    public void execute(Runnable command)
    {
        delegate().execute(command);
    }

    @Override
    public <T extends @Nullable Object> Future<T> submit(Callable<T> task)
    {
        return delegate().submit(task);
    }

    @Override
    public Future<?> submit(Runnable task)
    {
        return delegate().submit(task);
    }

    @Override
    public <T extends @Nullable Object> Future<T> submit(
            Runnable task, @ParametricNullness T result)
    {
        return delegate().submit(task, result);
    }
}
